In 3GPP Long-Term Evolution (LTE) networks, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of base stations, e.g., evolved Node-Bs (eNBs) communicating with a plurality of mobile stations referred as user equipments (UEs). A serving base station can communicate with a plurality of UEs in a serving cell via broadcasting, e.g., when UEs are in idle mode, or via dedicated unicasting, e.g., when UEs are in connected mode. In cellular networks, each serving cell periodically broadcasts its own system configuration—system information.
System information (SI) is information that is provided to users of a communication interface—user equipments (UEs). SI can include information that is needed before using the communication interface, information that is generally used by many users, and information that is suitable to be broadcast, e.g., used by users that are in idle mode. System information includes but is not limited to information that is provided by base stations or access points of a public land mobile network (PLMN), by transmission points, by beams, by cells, by cell portions, etc. System information could also be provided by other access points or by other UEs. The notation of UE also includes machine to machine communication scenarios, i.e., when there is no human user.
In current art, system information is acquired in each cell, where each cell repeatedly and always broadcasts system information. To work normally, UE should store and apply correct version of SI of its own serving cell. For the same SI type, different cells may have different configuration. In LTE, UE always re-acquire all SI types when it changes serving cell. However, periodic broadcast signaling increases inter-cell interference and thus limit the minimum cell distance and cell density. For high-frequency new systems, the concept of a piece of contiguous coverage is no longer a cell but instead a beam, which has very small coverage area. Periodic broadcasting overhead needs to be transmitted on multiple beam directions, resulting in multiple overhead.
5G new radio (NR) aims to reduce system information broadcast overhead. The potential of saving transmission in a higher frequency system by avoiding SI broadcasting is very large, especially at low traffic hours, when many beams will have zero active users, and the requirement for transmission of SI by broadcast is very low. Solutions to reduce SI broadcast overhead are sought.